In the pharmaceutical industry, the active ingredients in drugs are usually manufactured as crystalline solids, and a recurring problem is that of polymorphism. It has been suggested that producing the active pharma ingredients as room temperature ionic liquids could be advantageous. 

(a) What is polymorphism? 

(b) Why is polymorphism problematical to the pharmaceutical industry? 

(c) Distinguish between an ‘ionic liquid’ and a ‘room temperature ionic liquid’. Discuss some of the advantages that room temperature ionic liquids might have over crystalline solids in active pharma ingredients. 

(d) Hydrochloride salts, RNH₃Cl, or quaternary ammonium salts, R₄NCl, are common among active pharma ingredients. How would these be converted into ionic liquids? Comment on whether inorganic anions such as [AlCl₄]⁻ or [BF₄]⁻ would be suitable in these ionic liquids.